Transcript Slide 1

Geospatial Data Accuracy and the
New Mapping Accuracy Standard:
New Era
Session #35
Dr. Qassim Abdullah, Woolpert, Inc.
Pierre Le Roux, Aerometric, Inc.
Becky Morton, Towill, Inc.
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New ASPRS Positional Accuracy Standards
for
Digital Geospatial Data
Drafting Committee:
Chair: Douglas L. Smith, David C. Smith & Associates, Inc.
Dr. Qassim A. Abdullah, Woolpert, Inc.
Dr. David Maune, Dewberry
Karl Hans Heidemann, USGS
REVISION 7, VERSION 1 NOVEMBER 14, 2014
(FINAL BOARD APPROVAED Version)
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New ASPRS Positional Accuracy Standards
for
Digital Geospatial Data
 Replaces:
• ASPRS Accuracy Standards for Large-Scale Maps (1990)
• ASPRS Guidelines, Vertical Accuracy Reporting for Lidar
Data (2004)
 Developed by:
ASPRS Map Accuracy Standards Working Group, PAD, PDAD
and LIDAR joint committee for map accuracy standard update
 In Final Approved Version
• REVISION 7, VERSION 1, Nov. 14, 2014
• Approved and adopted by ASPRS during the board meeting
on Monday Nov. 17, 2014 in Denver during ASPRS 2014
PECORA conference
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New Standard for a New Era
Motivation Behind the New Standard:
• Legacy map accuracy standards, such as the ASPRS 1990
standard and the NMAS of 1947, are outdated. (over 30 years since
ASPRS1990 was written)
• Many of the data acquisition and mapping technologies that these
standards were based on are no longer used.
• More recent advances in mapping technologies can now produce
better quality and higher accuracy geospatial products and maps.
• Legacy map accuracy standards were designed to deal with plotted
or drawn maps as the only medium to represent geospatial data.
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New Standard for a New Era
• Within the past two decades (during the transition period
between the hardcopy and softcopy mapping environments),
most standard measures for relating GSD and map scale to the
final mapping accuracy were inherited from photogrammetric
practices using scanned film.
• New mapping processes and methodologies have become much
more sophisticated with advances in technology and advances in
our knowledge of mapping processes and mathematical
modeling.
• Mapping accuracy can no longer be associated with the camera
geometry and flying altitude alone (focal length, xp, yp, B/H ratio,
etc.).
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New Standard for a New Era
• New map accuracy is influenced by many factors such as:
– the quality of camera calibration parameters;
– quality and size of a Charged Coupled Device (CCD) used in the
digital camera CCD array;
– amount of imagery overlap;
– quality of parallax determination or photo measurements;
– quality of the GPS signal;
– quality and density of ground controls;
– quality of the aerial triangulation solution;
– capability of the processing software to handle GPS drift and
shift;
– capability of the processing software to handle camera selfcalibration,
– the digital terrain model used for the production of orthoimagery.
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• .
New Standard for a New Era
• These factors can vary widely from project to project, depending
on the sensor used and specific methodology. For these
reasons, existing accuracy measures based on map scale, film
scale, GSD, c-factor and scanning resolution no longer apply
to current geospatial mapping practices.
• Elevation products from the new technologies and active sensors
such as lidar and IFSAR are not considered by the legacy
mapping standards. New accuracy standards are needed to
address elevation products derived from these technologies.
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ASPRS Positional Accuracy Standards for
Digital Geospatial Data
– Applicability:
• Defines specific accuracy classes and associated RMSE
thresholds for digital orthoimagery, digital planimetric data, and
digital elevation data
• Intended to be technology independent
• Limited to accuracy thresholds and testing methodologies for any
mapping applications, and to meet immediate shortcomings in the
outdated 1990 and 2004 standards
• Is not intended to cover classification accuracy of thematic maps
• Does not specify the best practices or methodologies needed to
meet the accuracy thresholds
– Includes:
• Glossary, Symbols, examples, conversion to legacy standards
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New Standard Highlights
– Positional Accuracy Thresholds which are independent of
published GSD, map scale or contour interval
• digital orthoimagery
• digital elevation data
– Additional Accuracy Measures
• aerial triangulation accuracy,
• Ground controls accuracy,
• orthoimagery seam lines accuracy,
• lidar relative swath-to-swath accuracy,
• recommended minimum Nominal Pulse Density (NPD)
• horizontal accuracy of elevation data,
• delineation of low confidence areas for vertical data
• required number and spatial distribution of QA/QC check points
based on project area
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New Standard Highlights
– Positional Accuracy Thresholds which are independent of
published GSD, map scale or contour interval
• digital orthoimagery
• digital elevation data
– Additional Accuracy Measures
• aerial triangulation accuracy,
• Ground controls accuracy,
• orthoimagery seam lines accuracy,
• lidar relative swath-to-swath accuracy,
• recommended minimum Nominal Pulse Density (NPD)
• horizontal accuracy of elevation data,
• delineation of low confidence areas for vertical data
• required number and spatial distribution of QA/QC check points
based on project area
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New Standard Highlights
– It is All Metric!
– Unlimited Horizontal Accuracy Classes:
Horizontal Accuracy Standards for Geospatial Data
Horizontal
Accuracy
Class
RMSEx and
RMSEy (cm)
RMSEr (cm)
X-cm
≤X
≤1.41*X
Horizontal
Accuracy at 95%
Confidence Level
(cm)
≤2.45*X
Orthoimagery
Mosaic Seamline
Mismatch
(cm)
≤ 2*X
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Common Horizontal
Accuracy Classes
according to the new
standard[1]
Horizontal Accuracy
Class RMSEx and
RMSEy (cm)
RMSEr
(cm)
Orthoimage Mosaic
Seamline Maximum
Mismatch (cm)
Horizontal Accuracy at
the 95% Confidence Level
(cm)
0.63
0.9
1.3
1.5
1.25
1.8
2.5
3.1
2.50
3.5
5.0
6.1
5.00
7.1
10.0
12.2
7.50
10.6
15.0
18.4
10.00
14.1
20.0
24.5
12.50
17.7
25.0
30.6
15.00
21.2
30.0
36.7
17.50
24.7
35.0
42.8
20.00
28.3
40.0
49.0
22.50
31.8
45.0
55.1
25.00
35.4
50.0
61.2
27.50
38.9
55.0
67.3
30.00
42.4
60.0
73.4
45.00
63.6
90.0
110.1
60.00
84.9
120.0
146.9
75.00
106.1
150.0
183.6
100.00
141.4
200.0
244.8
150.00
212.1
300.0
367.2
200.00
282.8
400.0
489.5
250.00
353.6
500.0
611.9
300.00
424.3
600.0
734.3
500.00
707.1
1000.0
1223.9
1000.00
1414.2
2000.0
2447.7
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Common
Orthoimager
y Pixel Sizes
Examples on Horizontal
Accuracy for Digital
Orthoimagery interpreted from
ASPRS 1990 Legacy Standard.
0.625 cm
1.25 cm
2.5 cm
5 cm
7.5 cm
15 cm
Associated
Map Scale
1:50
1:100
1:200
1:400
1:600
1:1,200
ASPRS 1990
Accuracy
Class
Associated Horizontal
Accuracy According to
Legacy ASPRS 1990
Standard
RMSEx and
RMSEy (cm)
RMSEx and
RMSEy in
terms of
pixels
1
1.3
2-pixels
2
2.5
4-pixels
3
3.8
6-pixels
1
2.5
2-pixels
2
5.0
4-pixels
3
7.5
6-pixels
1
5.0
2-pixels
2
10.0
4-pixels
3
15.0
6-pixels
1
10.0
2-pixels
2
20.0
4-pixels
3
30.0
6-pixels
1
15.0
2-pixels
2
30.0
4-pixels
3
45.0
6-pixels
1
30.0
2-pixels
2
60.0
4-pixels
3
90.0
6-pixels
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Common
Orthoimage
ry Pixel
Sizes
1.25 cm
Digital Orthoimagery
Accuracy Examples for
Current Large and Medium
Format Metric Cameras
2.5 cm
5 cm
7.5 cm
15 cm
Recommended
Horizontal
Accuracy Class
RMSEx and
RMSEy (cm)
Orthoimage RMSEx and
RMSEy in terms of
pixels
Recommended use
≤1.3
≤1-pixel
Highest accuracy work
2.5
2-pixels
Standard Mapping and
GIS work
≥3.8
≥3-pixels
Visualization and less
accurate work
≤2.5
≤1-pixel
Highest accuracy work
5.0
2-pixels
Standard Mapping and
GIS work
≥7.5
≥3-pixels
Visualization and less
accurate work
≤5.0
≤1-pixel
Highest accuracy work
10.0
2-pixels
Standard Mapping and
GIS work
≥15.0
≥3-pixels
Visualization and less
accurate work
≤7.5
≤1-pixel
Highest accuracy work
15.0
2-pixels
Standard Mapping and
GIS work
≥22.5
≥3-pixels
Visualization and less
accurate work
≤15.0
≤1-pixel
Highest accuracy work
30.0
2-pixels
Standard Mapping and
GIS work
≥45.0
≥3-pixels
Visualization and less
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accurate work
Horizontal Accuracy/Quality Examples for High Accuracy Digital Planimetric
Data
Equivalent to map
scale in
ASPRS 2014
Horizontal
Accuracy Class
RMSEx and
RMSEy (cm)
RMSEr
(cm)
Horizontal
Accuracy at the
95% Confidence
Level (cm)
Approximate GSD of
Source Imagery (cm)
ASPRS
1990
Class 1
ASPRS
1990
Class 2
0.63
0.9
1.5
0.31 to 0.63
1:25
1:12.5
1:16
1.25
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
1.8
3.5
7.1
10.6
14.1
17.7
21.2
24.7
28.3
31.8
35.4
38.9
42.4
3.1
6.1
12.2
18.4
24.5
30.6
36.7
42.8
49.0
55.1
61.2
67.3
73.4
0.63 to 1.25
1.25 to 2.5
2.5 to 5.0
3.8 to 7.5
5.0 to 10.0
6.3 to12.5
7.5 to 15.0
8.8 to 17.5
10.0 to 20.0
11.3 to 22.5
12.5 to 25.0
13.8 to 27.5
15.0 to 30.0
1:50
1:100
1:200
1:300
1:400
1:500
1:600
1:700
1:800
1:900
1:1000
1:1100
1:1200
1:25
1:50
1:100
1:150
1:200
1:250
1:300
1:350
1:400
1:450
1:500
1:550
1:600
1:32
1:63
1:127
1:190
1:253
1:317
1:380
1:444
1:507
1:570
1:634
1:697
1:760
Equivalent to map
scale in NMAS
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New Standard Highlights
– Unlimited Vertical Accuracy Classes:
Vertical Accuracy Standards for Digital Elevation Data
Absolute Accuracy
Vertical
Accuracy
Class
RMSEz
NonVegetated
(cm)
NVA at 95%
Confidence
Level
(cm)
X-cm
≤X
≤1.96*X
Relative Accuracy (where applicable)
VVA at 95th
Percentile
(cm)
Within- Swath
Hard Surface
Repeatability
(Max Diff)
(cm)
Swath-toSwath
Non-Vegetated
Terrain
(RMSDz)
(cm)
Swath-toSwath
Non-Vegetated
Terrain
(Max Diff)
(cm)
≤3.00*X
≤0.60*X
≤0.80*X
≤1.60*X
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Vertical Accuracy/Quality Examples for Digital Elevation
Data
Absolute Accuracy
Relative Accuracy (where applicable)
Within-Swath
Hard Surface
Repeatability
(Max Diff)
(cm)
Swath-to-Swath
Non-Veg
Terrain
(RMSDz)
(cm)
Swath-to-Swath
Non-Veg
Terrain
(Max Diff)
(cm)
3
0.6
0.8
1.6
4.9
7.5
1.5
2
4
5.0
9.8
15
3
4
8
10-cm
10.0
19.6
30
6
8
16
15-cm
15.0
29.4
45
9
12
24
20-cm
20.0
39.2
60
12
16
32
33.3-cm
33.3
65.3
100
20
26.7
53.3
66.7-cm
66.7
130.7
200
40
53.3
106.7
100-cm
100.0
196.0
300
60
80
160
333.3-cm
333.3
653.3
1000
200
266.7
533.3
Vertical
Accuracy
Class
RMSEz
NonVegetated
(cm)
NVA
at 95%
Confidence Level
(cm)
1-cm
1.0
2.0
2.5-cm
2.5
5-cm
at
VVA
Percentile
(cm)
95th
17
Vertical accuracy of the new ASPRS 2014
standard compared with legacy standards
Vertical
Accuracy Class
RMSEz
Non-Vegetated
(cm)
Equivalent Class 1 contour
interval per ASPRS 1990
(cm)
Equivalent Class 2
contour interval per
ASPRS 1990 (cm)
Equivalent contour
interval per NMAS
(cm)
1-cm
1.0
3.0
1.5
3.29
2.5-cm
2.5
7.5
3.8
8.22
5-cm
5.0
15.0
7.5
16.45
10-cm
10.0
30.0
15.0
32.90
15-cm
15.0
45.0
22.5
49.35
20-cm
20.0
60.0
30.0
65.80
33.3-cm
33.3
99.9
50.0
109.55
66.7-cm
66.7
200.1
100.1
219.43
100-cm
100.0
300.0
150.0
328.98
333.3-cm
333.3
999.9
500.0
1096.49
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Examples on Vertical Accuracy and Recommended Lidar
Point Density for Digital Elevation Data according to the new
ASPRS 2014 standard
Absolute Accuracy
Recommended
Minimum NPD
(pts/m2)
Recommended
Maximum NPS7
(m)
2.0
≥20
≤0.22
2.5
4.9
16
0.25
5-cm
5.0
9.8
8
0.35
10-cm
10.0
19.6
2
0.71
15-cm
15.0
29.4
1
1.0
20-cm
20.0
39.2
0.5
1.4
33.3-cm
33.3
65.3
0.25
2.0
66.7-cm
66.7
130.7
0.1
3.2
100-cm
100.0
196.0
0.05
4.5
333.3-cm
333.3
653.3
0.01
10.0
Vertical Accuracy
Class
RMSEz
Non-Vegetated
(cm)
NVA
at 95% Confidence
Level (cm)
1-cm
1.0
2.5-cm
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Horizontal accuracy requirements for
elevation data
• Photogrammetric elevation data:, the horizontal
accuracy equates to the horizontal accuracy class that
would apply to planimetric data or digital orthoimagery
produced from the same source imagery, using the
same aerial triangulation/INS solution.
• Lidar elevation data: use the following formula:
𝐿𝑖𝑑𝑎𝑟 𝐻𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝐸𝑟𝑟𝑜𝑟 𝑅𝑀𝑆𝐸𝑟 =
tan(𝐼𝑀𝑈 𝑒𝑟𝑟𝑜𝑟)
𝐺𝑁𝑆𝑆 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛𝑎𝑙 𝑒𝑟𝑟𝑜𝑟 2 +
𝑥 𝑓𝑙𝑦𝑖𝑛𝑔 𝑎𝑙𝑡𝑖𝑡𝑢𝑑𝑒
0.55894170
2
20
Expected horizontal errors (RMSEr) for Lidar
data in terms of flying altitude
Altitude
(m)
Positional RMSEr
(cm)
Altitude
(m)
Positional RMSEr
(cm)
500
13.1
3,000
41.6
1,000
17.5
3,500
48.0
1,500
23.0
4,000
54.5
2,000
29.0
4,500
61.1
2,500
35.2
5,000
67.6
21
Low Confidence Areas in Lidar Dataset
Vertical
Accuracy
Class
Recommended
Project
Min NPD (pts/m2)
(Max NPS (m))
Recommended
Low Confidence
Min NGPD (pts/m2)
(Max NGPS (m))
Search Radius and
Cell Size
for Computing NGPD
(m)
Low Confidence
Polygons
Min Area
(acres (m2))
1-cm
≥20 (≤0.22)
≥5 (≤0.45)
0.67
0.5 (2,000)
2.5-cm
16 (0.25)
4 (0.50)
0.75
1 (4,000)
5-cm
8 (0.35)
2 (0.71)
1.06
2 (8,000)
10-cm
2 (0.71)
0.5 (1.41)
2.12
5 (20,000)
15-cm
1 (1.0)
0.25 (2.0)
3.00
5 (20,000)
20-cm
0.5 (1.4)
0.125 (2.8)
4.24
5 (20,000)
33.3-cm
0.25 (2.0)
0.0625 (4.0)
6.0
10 (40,000)
66.7-cm
0.1 (3.2)
0.025 (6.3)
9.5
15 (60,000)
100-cm
0.05 (4.5)
0.0125 (8.9)
13.4
20 (80,000)
333.3-cm
0.01 (10.0)
0.0025 (20.0)
30.0
25 (100,000)
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Accuracy requirements for aerial triangulation
and INS-based sensor orientation of digital
imagery
• Accuracy of aerial triangulation designed for digital planimetric
data (orthoimagery and/or digital planimetric map) only:
RMSEx(AT) or RMSEy(AT) = ½ * RMSEx(Map) or RMSEy(Map)
RMSEz(AT) = RMSEx(Map) or RMSEy(Map) of orthoimagery
• Accuracy of aerial triangulation designed for elevation data, or
planimetric data (orthoimagery and/or digital planimetric map) and
elevation data production:
• RMSEx(AT), RMSEy(AT)or RMSEz(AT) = ½ * RMSEx(Map), RMSEy(Map)or
RMSEz(DEM)
23
Accuracy requirements for ground
control used for aerial triangulation
• Accuracy of ground controls designed for planimetric
data (orthoimagery and/or digital planimetric
map)production only:
RMSEx or RMSEy = ¼ * RMSEx(Map) or RMSEy(Map),
RMSEz = ½ * RMSEx(Map) or RMSEy(Map)
• Accuracy of ground controls designed for elevation data,
or planimetric data and elevation data production:
RMSEx, RMSEy or RMSEz= ¼ * RMSEx(Map), RMSEy(Map) or
RMSEz(DEM)
24
Examples on Aerial Traingulation and
Ground Control Accuracy
Aerial Triangulation and Ground Control Accuracy Requirements,
Orthoimagery and/or Planimetric Data Only
Product Accuracy
(RMSEx, RMSEy, or
RMSEz)
(cm)
50
A/T Accuracy
Ground Control Accuracy
RMSEx and RMSEy
(cm)
RMSEz
(cm)
RMSEx and RMSEy
(cm)
RMSEz
(cm)
25
25
12.5
12.5
Aerial Triangulation and Ground Control Accuracy Requirements,
Orthoimagery and/or Planimetric Data and Elevation Data
A/T Accuracy
Ground Control Accuracy
Product Accuracy
(RMSEx, RMSEy)
(cm)
RMSEx and RMSEy
(cm)
RMSEz
(cm)
RMSEx and RMSEy
(cm)
RMSEz
(cm)
50
25
50
12.5
25
25
Reporting Horizontal Accuracy
• “This data set was tested to meet ASPRS Positional Accuracy
Standards for Digital Geospatial Data (2014) for a ___ (cm) RMSEx /
RMSEy Horizontal Accuracy Class. Actual positional accuracy was
found to be RMSEx = ___ (cm) and RMSEy = ___ cm which
equates to +/- ___ at 95% confidence level.”
• “This data set was produced to meet ASPRS Positional Accuracy
Standards for Digital Geospatial Data (2014) for a ___ (cm) RMSEx /
RMSEy Horizontal Accuracy Class which equates to +/- ___ cm at a
95% confidence level.”
26
Reporting Vertical Accuracy
• “This data set was tested to meet ASPRS Positional Accuracy
Standards for Digital Geospatial Data (2014) for a___ (cm) RMSEz
Vertical Accuracy Class. Actual NVA accuracy was found to be
RMSEz = ___ cm, equating to +/- ___ at 95% confidence level.
Actual VVA accuracy was found to be +/- ___ cm at the 95%
percentile.”
• “This data set was produced to meet ASPRS Positional Accuracy
Standards for Digital Geospatial Data (2014) for a ___ cm RMSEz
Vertical Accuracy Class equating to NVA =+/-___cm at 95%
confidence level and VVA =+/-___cm at the 95% percentile
27
Recommended Number of Check
Points Based on Area
Project Area (Square
Kilometers)
Horizontal Accuracy
Testing of Orthoimagery
and Planimetrics
Vertical and Horizontal Accuracy Testing of Elevation
Data sets
Total Number of Static
2D/3D Check Points
(clearly-defined points)
Number of Static
3D Check Points
in NVA
Number of Static
3D Check Points
in VVA
Total Number of
Static 3D Check
Points
≤500
20
20
5
25
501-750
25
20
10
30
751-1000
30
25
15
40
1001-1250
35
30
20
50
1251-1500
40
35
25
60
1501-1750
45
40
30
70
1751-2000
50
45
35
80
2001-2250
55
50
40
90
2251-2500
60
55
45
100
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New Standard Highlights
– Not Yet Addressed:
• Methodologies for accuracy assessment of linear features (as
opposed to well defined points)
• Rigorous total propagated uncertainty (TPU) modeling (as
opposed to -- or in addition to – ground truthing against
independent data sources)
• Robust statistics for data sets that do not meet the criteria for
normally distributed data and therefore cannot be rigorously
assessed using the statistical methods specified herein
• Image quality factors, such as edge definition and other
characteristics
• Robust assessment of check point distribution and density
• Alternate methodologies to TIN interpolation for vertical accuracy
assessment
29
Example on Applying the New
Standard
• User asked for orthoimagery with GSD =10 cm ortho,
what specifications he/she needs to ask for?
Answer:
1) According to the legacy standard of 1990, most probably will be:
Horizontal Accuracy RMSE = 20 cm (2 pixels) class I, Map scale =
1:800
2) According to the new Standard:
- RMSE = 10 cm (highest obtainable/"highest accuracy work“,
entails ground controls accurate to 2.5 cm and very accurate
workflow)
- RMSE = 20 cm ( comparable to 1990)
Practical specs: RMSE = 15 cm, no scale to be assigned
30
The Standard Web Site
• The final standard document is posted on
the web page:
http://www.asprs.org/PAD-Division/MapAccuracy-Standards-Working-Group.html
31
Thank You!
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